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number theory intermediate
Problem
The odd positive integers , are arranged into five columns continuing with the pattern shown on the right. Counting from the left, the column in which appears is the 
(A)
(B)
(C)
(D)
Solution
Considering each integer modulo gives the following pattern: We therefore observe that all numbers congruent to will appear in the second column, and since , the answer is .
Final answer
B